1/* 2 * libexif example program to display the contents of a number of specific 3 * EXIF and MakerNote tags. The tags selected are those that may aid in 4 * identification of the photographer who took the image. 5 * 6 * Placed into the public domain by Dan Fandrich 7 */ 8 9#include <stdio.h> 10#include <string.h> 11#include <libexif/exif-data.h> 12 13/* Remove spaces on the right of the string */ 14static void trim_spaces(char *buf) 15{ 16 char *s = buf-1; 17 for (; *buf; ++buf) { 18 if (*buf != ' ') 19 s = buf; 20 } 21 *++s = 0; /* nul terminate the string on the first of the final spaces */ 22} 23 24/* Show the tag name and contents if the tag exists */ 25static void show_tag(ExifData *d, ExifIfd ifd, ExifTag tag) 26{ 27 /* See if this tag exists */ 28 ExifEntry *entry = exif_content_get_entry(d->ifd[ifd],tag); 29 if (entry) { 30 char buf[1024]; 31 32 /* Get the contents of the tag in human-readable form */ 33 exif_entry_get_value(entry, buf, sizeof(buf)); 34 35 /* Don't bother printing it if it's entirely blank */ 36 trim_spaces(buf); 37 if (*buf) { 38 printf("%s: %s\n", exif_tag_get_name_in_ifd(tag,ifd), buf); 39 } 40 } 41} 42 43/* Show the given MakerNote tag if it exists */ 44static void show_mnote_tag(ExifData *d, unsigned tag) 45{ 46 ExifMnoteData *mn = exif_data_get_mnote_data(d); 47 if (mn) { 48 int num = exif_mnote_data_count(mn); 49 int i; 50 51 /* Loop through all MakerNote tags, searching for the desired one */ 52 for (i=0; i < num; ++i) { 53 char buf[1024]; 54 if (exif_mnote_data_get_id(mn, i) == tag) { 55 if (exif_mnote_data_get_value(mn, i, buf, sizeof(buf))) { 56 /* Don't bother printing it if it's entirely blank */ 57 trim_spaces(buf); 58 if (*buf) { 59 printf("%s: %s\n", exif_mnote_data_get_title(mn, i), 60 buf); 61 } 62 } 63 } 64 } 65 } 66} 67 68int main(int argc, char **argv) 69{ 70 ExifData *ed; 71 ExifEntry *entry; 72 73 if (argc < 2) { 74 printf("Usage: %s image.jpg\n", argv[0]); 75 printf("Displays tags potentially relating to ownership " 76 "of the image.\n"); 77 return 1; 78 } 79 80 /* Load an ExifData object from an EXIF file */ 81 ed = exif_data_new_from_file(argv[1]); 82 if (!ed) { 83 printf("File not readable or no EXIF data in file %s\n", argv[1]); 84 return 2; 85 } 86 87 /* Show all the tags that might contain information about the 88 * photographer 89 */ 90 show_tag(ed, EXIF_IFD_0, EXIF_TAG_ARTIST); 91 show_tag(ed, EXIF_IFD_0, EXIF_TAG_XP_AUTHOR); 92 show_tag(ed, EXIF_IFD_0, EXIF_TAG_COPYRIGHT); 93 94 /* These are much less likely to be useful */ 95 show_tag(ed, EXIF_IFD_EXIF, EXIF_TAG_USER_COMMENT); 96 show_tag(ed, EXIF_IFD_0, EXIF_TAG_IMAGE_DESCRIPTION); 97 show_tag(ed, EXIF_IFD_1, EXIF_TAG_IMAGE_DESCRIPTION); 98 99 /* A couple of MakerNote tags can contain useful data. Read the 100 * manufacturer tag to see if this image could have one of the recognized 101 * MakerNote tags. 102 */ 103 entry = exif_content_get_entry(ed->ifd[EXIF_IFD_0], EXIF_TAG_MAKE); 104 if (entry) { 105 char buf[64]; 106 107 /* Get the contents of the manufacturer tag as a string */ 108 if (exif_entry_get_value(entry, buf, sizeof(buf))) { 109 trim_spaces(buf); 110 111 if (!strcmp(buf, "Canon")) { 112 show_mnote_tag(ed, 9); /* MNOTE_CANON_TAG_OWNER */ 113 114 } else if (!strcmp(buf, "Asahi Optical Co.,Ltd.") || 115 !strcmp(buf, "PENTAX Corporation")) { 116 show_mnote_tag(ed, 0x23); /* MNOTE_PENTAX2_TAG_HOMETOWN_CITY */ 117 } 118 } 119 } 120 121 /* Free the EXIF data */ 122 exif_data_unref(ed); 123 124 return 0; 125} 126